In the case of motor vehicles, in particular ones with not very high engine power or motor vehicles with a manual-shift transmission, a semi-automatic or an automatic transmission with a low gear ratio which can, for example, be the case because the number of gears is small, a problem can arise that, under certain boundary conditions, starting is not possible solely with the engine intake torque. To enable starting in such a situation, a “turbine torque”, i.e., a boost pressure must be built up. In this way the boost pressure is built up by loading the engine with a time delay or at a climbing speed; so that there is a period during which the vehicle can roll backward because the driving force is lower than the driving resistance.
As a rule, before a starting process the driver cannot tell whether the vehicle will roll backward and that he should, therefore, apply the holding brake, and from which point in time he can release the holding brake without the vehicle rolling back.
This problem does not arise with vehicles having a starting aid or a roll-back preventer (“Hill holder”), since undesired rolling backward is prevented by, for example, co-operation of the transmission and the service brake. However, a prerequisite for most starting aids in motor vehicles is a correspondingly equipped brake system, which is not the case in the majority of vehicles. Furthermore, in most motor vehicles starting aids are an option which adds to the cost.
DE 10 200 783 C2 describes a starting-aid control device for use in a vehicle that comprises a manual-shift transmission, a holding brake, in particular an electro-mechanical or hydraulic holding brake, one or more detector devices for receiving signals, an evaluation unit for forming a signal that indicates a desire to start, and a control unit. In this case, when a signal indicating a wish to start occurs, a control element is actuated by the control unit in such manner that the holding brake is released and the evaluation unit evaluates a starting return-signal of the vehicle to determine the starting time; the parameters of inclination angle and wheel torque are evaluated to determine too early and/or too late an opening of the holding brake.
By virtue of the known starting-aid control device, by the evaluation of a few signals a starting process on a slope should be made easier since, by means of the starting-aid control device, a wish to start is recognized. Disadvantageously, however, this requires a brake system of complex structure that can be controlled by a control unit.